1. Technical Field
The present invention relates to a method for depositing a film and a method for manufacturing a semiconductor device.
2. Related Art
A proceeding of higher density device integration leads to a reduction of a gate insulating film thickness of a transistor. With such reduction in film thickness, an increase in gate leakage current is becoming a problem. In order to solve the problem, a method of reducing a leakage current is proposed by employing a high dielectric constant film (high-k film) as a gate insulating film, which allows reducing a physical film thickness while maintaining an electric film thickness.
Japanese Laid-open patent publication No. 2001-35842 (patent document 1) discloses a technology of reducing variations of film thickness occurred in depositing Ta2O5 or the like. As described in the document, a problem of causing the variations in the deposited film thickness due to a variation of a deposition rate, depending on a stand-by time after the deposition of Ta2O5 performed right before. The reason is considered that oxygen is eliminated in the stand-by time, and, in turn, when oxygen is introduced in a reaction chamber in the next depositing operation, oxygen is partially consumed on an interior surface of the reaction chamber, and eventually a quantity of oxygen supplied to a wafer is changed.
According to the document, one of solutions for such problem is to supply additional oxygen for compensation. Further, a method for inhibiting a variation in the film thickness by maintaining a pressure within the reaction interior at atmospheric pressure during the stand-by time is also proposed. This method utilizes phenomena that maintaining the pressure in the reaction chamber at a reduced pressure promotes an elimination of oxygen and on the contrary, maintaining the pressure in the reaction chamber at an atmospheric pressure inhibits an elimination of oxygen.